Passenger loading bridges are used to quickly transport passengers between an airport terminal and an aircraft and to protect the passengers from weather and other environmental influences. For example, a present day passenger loading bridge comprises a plurality of adjustable modules, including: a rotunda, a telescopic tunnel, a bubble section, a cab, and elevating columns with wheel carriage. Of concern to airlines is to ensure that a passenger loading bridge is aligned with an aircraft as rapidly as possible, thereby minimizing the time to complete passenger deplaning as well as the total time the aircraft spends at the airport terminal. As such, manual, semi-automated and fully-automated bridge alignment systems are known for adjusting the passenger loading bridge relative to the aircraft. Some passenger loading bridges are equipped with controls, which automatically cause the height adjustment mechanism of the passenger loading bridge to move the cab to a predetermined height depending on the aircraft model. However, a major problem is that once the cab of the passenger loading bridge is almost aligned with the door of the aircraft using an automated process, a bridge-operator still has to manually perform the final height adjustment. The reason is because one can retrieve data from memory relating the height of the doorsill to other features of the aircraft, but depending upon the load of the aircraft the height of the doorsill above ground varies substantially.
Schoenberger et al. in U.S. Pat. No. 5,226,204 describe an automated passenger loading bridge using video cameras to control bridge movement. The system maneuvers the cab of the bridge to a position close to the door of the aircraft, whereupon a bridge-operator controls the bridge movement by looking at images recorded by the video cameras. Suggestions are made in the patent specification that the system could be arranged to operate fully automated using image processing of the recorded video images to calculate the relative position of the passenger loading bridge with respect to the aircraft. However, image processing is time consuming, thus making the bridge movement based thereon slow.
U.S. Pat. No. 6,552,327 in the name of Anderberg, issued Apr. 22, 2003 teaches a device for positioning a passenger loading bridge for controlling at least the vertical movement of the bridge. The device comprises a sensor arranged to transmit electromagnetic radiation in different directions and to detect electromagnetic radiation. The device measures a time difference between the transmission of radiation in at least two different directions and the detection of said radiation for determining the position of the passenger loading bridge in relation to the aircraft. A major disadvantage of Anderberg's device is the need for highly complex sensor and signal processing systems, since accuracy of the positioning depends on the sensing and processing of very small time differences, in particular in situations of final vertical adjustments when the distance between the passenger loading bridge and the aircraft is relatively small.
PCT application WO 03/072435 in the name of Spencer et al., published Sep. 04, 2003 teaches an imaging system for a passenger loading bridge for docking automatically with an aircraft. Light is emitted toward reflective targets mounted to the aircraft. Using a digital camera the reflective light is sensed to provide image data of the targets. The image data are then processed to reveal information for bridge adjustment.
U.S. Patent Application 20030136898 in the name of Oki et al., published Jul. 24, 2003 teaches automatic control of a passenger loading bridge. Light is emitted towards reflective targets mounted to the aircraft. Using sensors the reflected light is sensed and based on the pattern of the sensed light the passenger loading bridge is adjusted.
The employment of reflective targets mounted to the aircraft has numerous disadvantages. Firstly, it is only possible to automatically adjust the passenger loading bridge for those aircraft having reflective targets mounted thereto. Secondly, reliable operation of the automatic adjustment is not always ensured, for example, foreign material that is disposed on the reflective targets, separation of the reflective targets from the aircraft, or adverse weather conditions can substantially impede the performance of this system, or even render it completely inoperative. Furthermore, there also exists the danger that reflective surfaces of ground service equipment or other ramp equipment may inadvertently be mistaken for an aircraft.
It would be advantageous to provide automated elevational adjustment of a passenger loading bridge that is accurate and fast in response for final height adjustment. It would be further advantageous to provide automated elevational adjustment of a passenger loading bridge that is simple, reliable, and does not require modifications of the aircraft serviced by the passenger loading bridge.